Surgical instrument set and procedure for implanting sound transducer proximate to patient&#39;s outer ear canal

ABSTRACT

A hearing aid system ( 10 ) including an implantable device ( 60 ), and a surgical instrument ( 134 ) for enabling a physician to install the implant ( 60 ) in a patient&#39;s body in a simple office procedure using only local anesthesia.

FIELD OF THE INVENTION

This invention relates generally to hearing aid systems and moreparticularly to an implantable hearing aid device and a compatiblemethod and surgical instrument set useful for implanting the device toproject sound energy into a patient's outer ear canal.

BACKGROUND OF THE INVENTION

International application PCT/US2003/035348, which is incorporatedherein by reference, describes a hearing aid system including an implantconfigured for placement in a recess formed between a patient'sretro-auricular space and outer ear canal. The implant is described ascomprising a case containing an antenna, electronic circuitry, and atransducer. The transducer functions to convert electrical signalssupplied from the implant electronic circuitry into sound energy forprojection into the patient's ear canal.

The hearing aid system described in said application PCT/US2003/035348also includes a microphone module including a microphone, electroniccircuitry and an antenna. Sound energy picked up by the microphoneproduces an output signal which is processed by the module electroniccircuitry and transmitted by a telemetry link, preferably RF, to theimplant. The signal received by the implant may then be furtherprocessed by the implant electronic circuitry to cause the implanttransducer to project sound energy into the patient's outer ear canal.

International application PCT/US2004/011079, which is incorporatedherein by reference, describes an implantable percutaneous device, andmethod of implantation, especially configured to promote soft tissueingrowth for creating an infection resistant barrier and for anchoringthe implanted device in place.

SUMMARY OF THE INVENTION

The present invention is directed to a hearing aid system, including animplantable device (“implant”) and a surgical instrument set forenabling a physician to install the implant in a patient's body in asimple procedure, typically using only local anesthesia, whileminimizing surgical time, trauma and cost. More particularly, theinvention is directed to a hearing aid system including a deviceconfigured for implantation and anchoring in subcutaneous tissueadjacent to a percutaneous hole opening into a patient's ear outercanal.

In accordance with a preferred embodiment of the invention, a surgicalinstrument set is provided including a cannula having an elongate shaftcomprised of an outer wall surrounding an elongate interior lumen. Thedistal end of the shaft is preferably configured with a bevel, orchisel, edge to enable the physician to tunnel the edge throughsubcutaneous tissue to position the edge proximate to the patient'souter ear canal. A preferred cannula embodiment in accordance with theinvention carries external markings comprising a linear scale, or depthguide, viewable by the physician during the subcutaneous tunnelingprocess. This depth guide allows the physician to accurately place theshaft distal end just short of the patient's ear canal, e.g., by 2-3 mm.

The cannula lumen has an entrance opening at its proximal end and anexit opening at its distal end to permit instruments to extendtherethrough. However, in accordance with a preferred cannulaembodiment, a movable door is mounted adjacent to the exit opening toprevent tissue intrusion. The door is preferably configured to be hingedclosed as the cannula is advanced during the tunneling process buthinged open when pushed by an instrument passed through the cannulalumen toward the distal end.

In a preferred method of implantation in accordance with the invention,the cannula is held in place by the physician and an elongate holeforming tool is inserted through the cannula's lumen. The hole formingtool preferably comprises a handle and a shank having a cutting edge atits distal end. The preferred hole forming tool is configured so that itcan be axially rotated in the cannula to axially advance the cuttingedge to cut a percutaneous hole opening into the patients ear canal.Alternatively, the hole can be punched. Regardless, it is preferable thecutting edge work against an anvil, or cutting board, surfacetemporarily placed into the patient's ear canal to form a clean hole.

Also in accordance with a preferred method of implantation, the implantis transported through the cannula lumen to the exit opening foranchoring in subcutaneous tissue proximate to the patient's ear canal.The implant preferably comprises a housing, or case, having a peripheralsurface area carrying a porous layer, e.g., titanium mesh, configured topromote tissue ingrowth for anchoring the implant.

A cannula in accordance with a preferred embodiment of the inventioncomprises an elongate shaft having an outer wall of noncircular, e.g.,oval, cross section. This noncircular cross-section facilitates taperingthe cannula shaft distal end to form a flat bevel, or chisel, edgeuseful for separating skin from bone as the shaft distal end is manuallyadvanced by the physician from a retro-auricular incision to a positionproximate to the patient's ear canal.

The cannula noncircular outer wall also facilitates the formation of anoncircular interior lumen. The implant housing preferably has a similarnoncircular cross-section which allows it to translate along the cannulalumen toward the exit opening without rotating.

The implant housing preferably comprises a body having a laterallyoriented shoulder and a distally projecting stud for extendingpercutaneously through the hole opening into the ear canal. Exteriorsurface areas of the shoulder and/or stud and/or body preferably carryporous material for encouraging soft tissue ingrowth to assist inanchoring the housing.

A preferred cannula in accordance with the invention includes a springloaded latch carrying an index tooth engageable with various instrumentsinsertable through the cannula lumen. A preferred instrument set inaccordance with the invention includes an obturator for blocking thedistal end of the cannula lumen when the cannula is being tunneledthrough tissue. The cannula index tooth preferably engages a matinggroove in the obturator to releasably fix the obturator to the cannula.

The preferred instrument set also includes a dilator, insertable throughthe cannula lumen, for pushing tissue away from the lumen exit openingin preparation for using the aforementioned hole forming tool.

The preferred hole forming tool (or “hole former”) includes a handle anda hollow shank having a cutting edge at its distal end. A helicalgroove, or thread, in the tool handle is configured to receive thecannula index tooth to initially locate the cutting edge at a startingposition adjacent to the tissue surrounding the patient's ear canal. Thephysician is then able to axially rotate the handle to axially advancethe helical groove relative to the filed index tooth, thereby advancingthe cutting edge to form a percutaneous hole through the tissuesurrounding the patient's ear canal.

The hollow shank of the hole forming tool contains a lumen whichaccommodates a rod adapted to be pushed distally through the shank forejecting any tissue captured by the shank distal end.

The preferred instrument set further includes an inserter instrumentcomprising a handle defining a bore for receiving the implantabledevice. The inserter handle works in cooperation with the cannula and apusher tool. The pusher tool is used to push the implant out of theinserter handle and along the cannula lumen to a position proximate tothe patient's ear canal to project the implant's stud percutaneouslyinto the ear canal.

The preferred instrument set preferably also includes a speculum usefulby the physician during the implant procedure for spreading thepatient's ear canal to enhance visibility while also presenting ananvil, or cutting board, surface for the tool cutting edge to engage.

Further, a push-back tool is preferably provided which the physician caninsert into the patient's ear canal to engage and properly position thepercutaneously extending stud.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a block diagram of an exemplary hearing aid system including amicrophone module and an implantable electroacoustic transducer devicefor projecting sound energy into a patient's ear canal;

FIGS. 2A, 2B, and 2C are respectively end, top, and side views of apreferred implantable device in accordance with the invention;

FIG. 3 schematically illustrates a patient's ear area depicting theposition of the ear canal and indicating the use of a cannula instrumentin accordance with the invention for subcutaneously implanting thetransducer device to project sound from a stud extending percutaneouslyinto to the patient's outer ear canal;

FIG. 4 illustrates members (i.e., a cannula, an obturator, a dilator, ahole former, an implant inserter, and a pusher) of a preferred surgicalinstrument set in accordance with the invention useful for implantingthe device of FIGS. 2A, 2B, and 2C;

FIGS. 5A, 5B, 5C, and 5D illustrate the preferred cannula where FIG. 5Ais a top view, FIGS. 5B and 5C are sectional views taken substantiallyalong planes 5B-5B and 5C-5C, and FIG. 5D is an enlarged view of thedistal end of the cannula;

FIG. 6A illustrates the preferred obturator extending through thecannula shaft and FIG. 6B depicts the cannula/obturator tunnelingthrough tissue to position the cannula distal end proximate to apatient's ear canal;

FIGS. 7A and 7B illustrate the preferred dilator extending through thecannula shaft and FIGS. 7C and 7D are enlarged views showing the cannuladistal end;

FIGS. 8A, 8B, 8C, and 8D illustrate the preferred hole former where FIG.8A shows the hole former inserted in the cannula shaft but not yetengaged with the cannula index tooth, FIG. 8B shows the index toothengaged with a threaded groove on the hole former, FIG.8C shows the holeformer having advanced along the cannula shaft to cause its distalcutting edge to form a percutaneous hole opening into the ear canal, and

FIG. 8D shows a rod extending through the hole former shaft for ejectingtissue from is distal end;

FIGS. 9A and 9B illustrate the preferred inserter and pusher fortransporting the implant through the cannula shaft to a positionproximate to the patient's ear canal with the implant's distallyprojecting stud extending into the ear canal;

FIGS. 10A and 10B illustrate a speculum useful by a physician during theimplantation procedure for stretching the patient's ear canal to enhancevisibility while also presenting an anvil, or cutting board, surface forthe hole former cutting edge to engage;

FIG. 11 illustrates an alternate speculum for presenting a cutting boardsurface to the hole former cutting edge;

FIG. 12 illustrates a push-back tool useful for positioning thepercutaneous stud in the patient's ear canal; and

FIGS. 13A, 13B, and 13C illustrate an alternative implant in accordancewith the invention characterized by anchors carried by the implanthousing for anchoring the housing in body tissue.

DETAILED DESCRIPTION

Attention is initially directed to FIG. 1 which illustrates a hearingaid system 10 of the type disclosed in aforementioned U.S. internationalapplication PCT/US2003/0353348, which system can advantageously employthe teachings of the present invention. The exemplary system 10 includesan implantable device (or “implant”) 60 comprising a housing or case 61.The structural aspects of a preferred housing 61 are illustrated inFIGS. 2A, 2B and 2C to be discussed hereinafter. In addition to theimplant 60, the exemplary system 10 contemplates utilization of anexternal microphone module 70 capable of communicating via a telemetrylink 76 with an antenna 64 mounted within the implant housing 61. Theantenna 64 is coupled to electronic circuitry 72 contained within thehousing 61. More particularly, the antenna 64 is coupled to signalprocessing circuitry 67 via telemetry circuitry 69. The implant housing61 also includes a power source 66, typically a battery, for supplyingpower, via power management circuitry 71, to the signal processingcircuitry 67 and telemetry circuitry 69. The signal processing circuitry67 drives an electroacoustic transducer 65, e.g., a speaker, to producesound energy 78.

In typical operation of the exemplary system 10 of FIG. 1, themicrophone module 70 is worn externally by a patient and converts soundenergy to an RF telemetry signal. 76 representing audio information inanalog or digitally encoded form. This RF signal is transmitted to theimplant antenna 64 and coupled to the electronic circuitry 72 forprocessing. The telemetry circuitry 69 includes a receiver (not shown)to acquire, filter, and process the incoming signal. The antenna 64 mayadditionally receive charging electromagnetic energy to charge the powersource 66. This energy is transmitted via the telemetry circuitry 69 tothe power management circuitry 71. The system 10 may also include aremote control device 75, e.g., a hand held controller, which can beused by the patient to supply commands, via antenna 64, to the signalprocessing circuitry 67 for affecting various operational parameterssuch as volume, equalization profile, etc.

FIGS. 2A, 2B and 2C illustrate a preferred implant housing 61 inaccordance with the present invention. The housing 61 basicallycomprises a hollow structure 100 comprised of a body portion 102 and adistally extending stud 104. The body portion 102 comprises an outerwall defining a peripheral wall surface 105 and a proximal end wallsurface 106.

The peripheral surface 105 extends from the proximal end wall surface106 to a lateral shoulder surface 108. Stud 104, defining peripheralwall surface 107, extends distally from the shoulder surface 108terminating at distal end wall surface 109. The housing peripheralsurface 105 preferably defines a noncircular cross-section, e.g., oval,for mating with a similarly shaped surgical instrument lumen to bedescribed hereinafter. The stud peripheral surface 107 preferablydefines a circular cross-section. As can be seen in FIGS. 2A, 2B and 2C,the housing surfaces, e.g., peripheral surface 107 and lateral shouldersurface 108 preferably carry a layer of porous material 112, e.g.,titanium mesh, for promoting tissue ingrowth for retaining the housing61 in place after implantation.

Attention is now directed to FIG. 3 which generally illustrates the eararea of a patient, and the position of the patients ear canal 130. FIG.3 also depicts the distal portion of a hollow shaft 132 of a surgicalinstrument (cannula) 134 to be discussed in detail hereinafter. As willbe described, the instrument 134 is used to tunnel through the patientssubcutaneous tissue to create a path for transporting the implanthousing 61 to a recess adjacent to the ear canal 130. More particularly,as will be discussed hereinafter, in accordance with the presentinvention, the distal end 136 of shaft 132 is advanced along a path 140from an incision 138 behind the patients pinnace to an implant siteproximate to the ear canal 130. Thereafter, the hollow shaft 132 is usedto transport the implant housing 61 to the implant site such that theimplant housing stud 104 can percutaneously extend into the canal 130for projecting sound energy directly into the patient's ear canal.

Attention is now directed to FIG. 4 which illustrates perspective viewsof members of a preferred surgical instrument set useful for enabling aphysician to readily implant the device 60. The preferred instrument setincludes the cannula 134, an obturator 152, a dilator 154, a hole former156, an implant inserter 158 and a pusher 160. Additional instrumentsuseful in the implant procedure may include a speculum configured toprovide an anvil or cutting board surface (FIGS. 10A, 10B, 11) and apositioning, or push-back tool (FIG. 12).

Attention is now directed to FIG. 5A and 5B which illustrate thepreferred cannula 134 for forming a tunnel 140 as shown in FIG. 3 fortransporting the implant device '60 to a desired location proximate tothe patient's ear canal 130. The cannula 134 having a proximal end 162and a distal end 163 is comprised of a handle 164 and an elongate shaft165. An entrance opening 169 at the proximal end 162 opens into aninterior bore 170. The bore 170 communicates with interior lumen 172extending through the elongate shaft 165 to an exit opening 174 at thecannula distal end 163.

The distal end 163 of shaft 165 is preferably beveled along plane 175and forms a chisel edge 176. As shown in FIG. 5C, the shaft wall 180preferably has a noncircular, e.g., oval, cross-section. Optionally, athin strip of flexible metal 182 is provided to overlay the upperexterior surface 183 of shaft 165 and bend downwardly at its distal endto form a door 184. The door 184 overlays and normally substantiallycloses the lumen exit opening 174. The strip 182 is preferablysufficiently flexible to enable the door 184 to be pushed open by amember from within the lumen 172, as will be discussed hereinafter.

Markings 186, comprising a linear scale, are preferably formed along theupper exterior shaft surface 183 and/or the surface of strip 182, forindicating to the physician the depth of subcutaneous penetration of theshaft distal edge 176.

The cannula handle 164 preferably includes a finger operated latch 188mounted for pivotal movement around pin 190. A spring 192 normallybiases the latch 188 in a counter clockwise direction (as viewed in FIG.5B) to urge an index tooth 194 through opening 195 into bore 170. Aswill be seen hereinafter, the index tooth 194 is used to operativelylatch various members of the preferred instrument set (FIG. 4) to thecannula 134 in the course of performing the implant procedure.

Attention is now called to FIG. 6A which depicts the obturator 152mounted in the cannula 134. Note that the obturator comprises a handle196 having a rod 198 extending therefrom. The rod carries a dilatorblock 199 at its distal end which is insertable through cannula bore 170for passage through lumen 172 for positioning adjacent to door 184. Theblock 199 has a cross-section shaped and dimensioned to substantiallyfully occupy the lumen 172 and is beveled to conform to the bevel plane175 at the front of cannula shaft 165. When the obturator rod 198 andblock 199 are inserted through bore 170, shoulder 200 on the obturatorhandle 196 engages interior surface 202 of cannula 134 and/or indextooth 194 falls into a recess 203 in the obturator handle. This actionlocates block 199 immediately behind the door 184.

With the obturator 152 mated with the cannula 134 (FIG. 6A), thephysician will typically begin the implant procedure by forming a 2 cmskin incision 138 behind the pinnace, approximately 4 cm posterior tothe ear canal 130 at an angle of roughly 30° to a horizontal lineradiating from the center of the ear canal.

The physician will then use the mated cannula/obturator to tunnel fromthe skin incision to a location proximate to the ear canal. The chiseledge 176 functions to separate subcutaneous tissue 204 (FIG. 6B) frombone 205 as the physician presses the handle 196 to advance edge 176toward the ear canal. Tunneling typically continues until the physicianobserves tenting or skin protrusion within the ear canal. The depthmarkings 186 can be used as a guide during tunneling to assist thephysician. It is preferable,that tunneling terminate when the edge 176is approximately 2-3 mm short of the ear canal. During tunneling, thedoor 184 simply lays flat against the beveled end of block 199 andcannula shaft 165.

After the edge 176 reaches the desired location, the obturator 152 iswithdrawn from the cannula proximal end leaving the cannula 134 inplace. The physician then will insert the dilator 154 through thecannula lumen 172 as shown in FIG. 7A. The dilator 154 is comprised of ahandle 210 and a forwardly projecting shaft 212. The shaft 212terminally carries a dilator block 214. The dilator shaft 212 and block214 are inserted through the cannula bore 170 and shaft lumen 172towards the door 184. Note in FIG. 7A that the dilator handle 210defines a recess, or groove, 216 positioned to receive cannula indextooth 194. FIG. 7A depicts the dilator 154 partially inserted intocannula 134 whereas FIG. 7B shows the dilator fully inserted with theindex tooth 194 clicked into the dilator groove 216. Note in FIG. 7Bthat with the index tooth 194 and groove 216 engaged, the dilator shaft212 positions the block 214 so that it opens the door 184. The dilatorblock 214 is tapered at surface 218 and can be used in either of twoopposite orientations, respectively shown in FIGS. 7C and 7D. In thefirst orientation (FIG. 7C), the tapered surface 218 is shown facing thedoor 184. In the second orientation (FIG. 7D), the tapered surface 218is remote from the door 184 and instead the square surface 220 of thedilator block 214 faces the door. The function of the dilator 154 is topush tissue away from the open distal end of the cannula 134 so that thesubsequently used hole former 156 need only cut through tissue directlyin front of the cannula edge 176. Depending upon the nature of thetissue to be dilated, the physician may choose to use the dilator block218 as shown in FIG. 7C for gentle dilation or as shown in FIG. 7D formore aggressive dilation.

After dilation of the subcutaneous tissue, the dilator 154 is removedfrom the cannula 134 which remains in situ. Thereafter, the hole former156 is installed into the cannula 134. FIG. 8A shows the hole former 156partially inserted into the cannula 134. FIG. 8B shows the hole former156 fully inserted into the cannula but with its cutting edge still in aretracted non-cutting position. FIG. 8C shows the hole former 156 withits cutting edge advanced for cutting a percutaneous hole into the earcanal. FIG. 8D shows a rod within the hole former shank being advancedto eject any tissue captured by the shank cutting edge.

More particularly, the hole former 156 is comprised of a handle 240including an enlarged knurled portion 242 and a reduced portion 246. Ahollow shank 250 extends distally from the reduced portion 246. Theshank 250 at its distal end is provided with a cutting edge 252preferably forming a circular periphery.

A helical groove 254 is formed on the outer surface of the reducedhandle portion 246. The groove 254 is dimensioned to accommodate theindex tooth 194 carried by the cannula latch 188. In use, the holeformer 156 is inserted through the cannula entrance opening 169 intobore 170 until the index tooth 194 clicks into a distal thread of thehelical groove 254, as shown in FIG. 8B. When so engaged, the distal endof the shank 250 opens the door 184 placing the cutting edge 252 a shortdistance from the tissue surrounding the ear canal 130. The physician isthen able to axially rotate the handle 242 to thread groove 254 withrespect to the fixed tooth 194 to axially advance the shank 250 and thusmove the cutting edge 252 to the ear canal wall. In order to cleanly cuta hole 253 through the ear canal wall, it is preferable to insert ananvil, or cutting board, surface 260 within the ear canal for thecutting edge 252 to bear against. In use, the physician will carefullyobserve the interior of the ear canal as he rotates handle 242 toadvance the cutting edge 252. The helical groove 254 is typically formedso that the total axial movement available from FIG. 8B to FIG. 8C issmall, e.g., 5-6 mm. Typically, the physician inserts the anvil when hefirst observes tissue tenting within the ear canal. Speculum embodimentsproviding the anvil, or cutting board, surface will be discussed laterin conjunction with FIGS. 10A, 10B, and 11.

The helical coil 254 is preferably configured so that an initial amountof rotation axially advances cutting edge 252 (mode 1) and additionalrotation freely spins the cutting edge (mode 2). That is, once thethreaded groove 254 has advanced to the position shown in FIG. 8C, thehandle 242 can be rotated back and forth to freely spin the cutting edge252 to cleanly cut the hole through to the ear canal. Although referencehas been made to “cutting” the hole, it should be understood that thehole can be alternatively formed, e.g., punching.

Once the hole has been formed any tissue captured within the lumen ofthe shank 250 can be ejected by pressing an ejector button 264 mountedadjacent the handle portion 242. Note that the ejector button is securedto an axial rod 266 which extends through the lumen of hollow shank 250.A spring 268 retained in recess 270 in handle portion 242 biases thebutton 264 to the left as shown in FIGS. 8A, 8B, and 8C. Note however inFIG. 8D that the button 264 has been manually pushed to the right intothe recess 270, compressing spring 268, to thrust rod 266 forwardly pastthe shank cutting edge 252. This action ejects any tissue plug capturedwithin the shank 250. The physician then can readily retrieve the plugfrom the ear canal with forceps. Typically, the physician prefers toeject the plug into the ear canal before removing the hole former 156from the cannula 134 so that the plug is not lost when the cannula issubsequently removed.

After the hole former 156 is removed from the cannula 134, the inserter158 is inserted into the cannula bore 170 as depicted in FIG. 9A. Priorto installing the inserter 158 into the cannula, the implant housing 61is placed within a bore 280 of the inserter 158. Note that the inserterhas an exterior recess 282 formed thereon for receiving the index tooth194 carried by the spring urged latch 188. The inserter bore 280 is openat its proximal end 283 so that the shaft 284 of the aforementionedpusher 160 can be inserted therethrough as shown in FIG. 9B. The pushershaft 284 is attached to a pusher handle 286. The shaft 284 ispreferably provided with a threaded helical groove 290 configured tomate with a tooth 292 carried by the inserter and extending into theinserter bore 280. Thus, by turning the pusher handle 286 relative tothe inserter 158, the pusher shaft 184 will advance axially as thehelical groove 290 is threaded relative to the tooth 292. This axialadvance enables the shaft 284 to transport the implant device 60 throughthe cannula lumen 172 to a position proximate to the ear canal. Aspreviously mentioned, the cannula lumen 172 and the implant devicehousing preferably have corresponding non-circular cross-sections whichassures that the device housing does not rotate as it is transportedthrough the cannula lumen 172. The device 60 will arrive at the earcanal 130 properly positioned for the device. stud 104 to projectthrough the percutaneous hole 253 previously formed in the ear canal asrepresented in FIG. 8C.

Attention is now directed to FIG. 10A and 10B which illustrate apreferred right angle speculum 300 useful by the physician to spread thepatient's ear canal for better visibility when using the aforedescribedhole former tool 156. The speculum 300 is comprised of a base member 302and a slide member 303. The base member 302 comprises a flat metal striphaving an intermediate portion 304, a downwardly bent rear portion 306,and an upwardly bent forward portion, or jaw, 308. The jaw 308 carriesan anvil, or cutting board, member 310.

The speculum 300 slide member 303 includes a flat intermediate portion314 which overlays the base member intermediate portion 304. The rearportion of slide member 303 is bent downwardly at 314 extending throughbase member slot 315 to form a loop 316 for receiving a user's indexfinger. The forward end of slide member 314 is bent upwardly to form ajaw 318.

The physician will typically use the speculum 300 in conjunction withusing the hole former 156 by placing the speculum jaws 308 and 318 inthe patient's ear canal. The cutting board 310 is aligned with theanticipated location of the percutaneous hole 253. The physician willthen place his thumb against the rear portion 306 of base member 302 andhis index finger through loop 316. By squeezing the thumb and indexfinger, the slide member 303 will move rearwardly (to the right asviewed in Figured 10B) to spread jaws 308 and 318. The spreading of thejaws will spread the ear canal to improve visibility and also place thecutting board in a position to be engaged by the cutting edge 252 toform a clean percutaneous hole.

FIG. 11 illustrates an alternative speculum 340 including members 342and 344 mounted for hinged movement around pin 346. Member 342 iscomprised of a handle portion 350 and a jaw portion 352. Member 344 issimilarly comprised of a handle portion 354 and a jaw portion 356.

In use, the physician will insert the jaw portions 352 and 356 into thepatient's ear canal. By squeezing the handle portions 350 and 354, thejaw portions 352 and 356 move apart to spread the patient's ear canal toincrease visibility. In accordance with the present invention, at leastone of the jaw portions carries an anvil, or cutting board, member 360to provide a surface for engagement by the hole former cutting edge asrepresented in FIG. 8C.

FIG. 12 illustrates a positioning or push back tool 400. The tool 400 iscomprised of a handle 402 and a shaft 404 carrying a flat disk 406 atits distal end. The tool 400 can be used by the physician by insertingthe disk 406 into the patient's ear canal to engage the percutaneouslyextending implant stud 104 to push back and properly position the studend face in the ear canal.

FIGS. 13A, 13B and 13C illustrate a modification of the implant housing61 shown in FIGS. 2A, 2B and 2C to achieve enhanced anchoring ifdesired. The housing 61 of FIGS. 13A, 13B, 13C utilizes additionalporous material 112 extending proximally from the shoulder 108 over agreater area of the peripheral surface 105 of body portion 102.Additionally, to facilitate device anchoring prior to adequate tissuegrowth into the porous layer 112, one or more fixation arms, or anchors,120 is provided. Each arm 120 has a first free end 122 and a second end124 secured to the housing body portion 102. Each arm 120 is preferablyformed of flexible material so it can be pressed to a retracted positionagainst the peripheral surface of body portion 102 prior to beingejected from the cannula lumen, as represented in FIG. 9B. As depictedin FIGS. 13A, 13B, and 13C, the arms 120 will deploy by extendingoutwardly for engaging subcutaneous body tissue to better anchor thehousing 61.

FIG. 13C schematically depicts a sectional view through the housing 61to show an exemplary placement of components within the housing. Moreparticularly the housing 61 encloses a sealed internal compartmentcontaining at least one circuit board 126. The circuit board 126 cancarry a planar antenna 64 connected to a power source 66 in the form ofa disc shaped battery. An electroacoustic transducer 65 is mountedwithin the portion of compartment 125 extending into stud 104 forprojecting sound energy through stud end wall 109.

From the foregoing, it should now be appreciated that an improvedhearing aid system has been disclosed herein which enables theimplantation of a hearing aid in a tunnel or recess adjacent to apatient's ear canal for positioning a sound transducer to project soundthrough a percutaneous hole directly into a patient's outer ear canal.By utilization of the simple instrument and procedure disclosed herein,the described hearing aid can be readily deployed in a physician'soffice procedure with little or no insult to the tissue adjacent to theear canal.

Although a specific embodiment of the invention has been disclosedherein, it should be recognized that variations and modifications willoccur to those skilled in the art well within the spirit and intendedscope of the invention as defined by the appended claims.

1. A method for implanting a hearing aid in a patient so as to extend percutaneously into the patient's outer ear canal, said method comprising: providing an elongate shaft having an outer wall surrounding at least one elongate lumen extending through said shaft to a distal end; tunnelling said shaft from a location behind the patient's pinnace to position said shaft distal end in subcutaneous tissue proximate to said patients ear canal; inserting an elongate tool through said lumen so as to position a tool cutting edge proximate to shaft distal end; advancing said tool cutting edge past said shaft distal end to form a percutaneous hole opening into said ear canal; providing a hearing aid housing having a stud projecting therefrom; and transporting said housing through said lumen to said shaft distal end to position said stud in said percutaneous hole opening into said ear canal.
 2. The method of claim 1 wherein a porous layer is provided on the peripheral surface of at least a portion of said housing for promoting tissue ingrowth.
 3. The method of claim 1 wherein said tunnelling step includes providing an obturator to close said lumen proximate to said shaft distal end.
 4. The method of claim 1 further including inserting an anvil in said patient's ear canal; and wherein said step of advancing said tool cutting edge includes engaging said cutting edge against said anvil.
 5. The method of claim 1 wherein said housing carries at least one anchor configured for movement between a retracted position and a deployed position; and wherein when said housing is being transported through said lumen said anchor is retracted and when said housing engages said subcutaneous tissue said anchor is deployed to retain said housing adjacent to said percutaneous hole.
 6. The method of claim 1 wherein said step of providing said elongate shaft includes providing a shaft having a flat bevel edge at its distal end for facilitating the separation of skin from bone while tunneling.
 7. The method of claim 1 wherein said step of providing an elongate shaft includes providing a shaft outer wall having a noncircular cross-section.
 8. The method of claim 1 wherein said step of providing an elongate shaft includes providing an elongate lumen having a noncircular cross-section.
 9. The method of claim 8 wherein said step of providing a hearing aid housing includes providing a housing having a noncircular cross-section corresponding to said lumen cross-section.
 10. The method of claim 1 further including providing a movable door for normally closing the open distal end of said shaft; and wherein said step of inserting said tool through said lumen to said distal end acts to open said door.
 11. The method of claim 1 including the further step of inserting a tool into said ear canal for pushing said stud back into a desired position relative to said ear canal.
 12. The method of claim 1 wherein said step of providing an elongate shaft includes providing visible depth markings on said shaft for facilitating the positioning of said shaft distal end proximate to said patent's ear canal.
 13. A medical device configured for implantation at a subcutaneous site in a patient's body comprising: a housing defining a body portion configured for mounting subcutaneously proximate to a patient's ear canal and a stud portion extending from said body portion for percutaneously projecting into said ear canal; said body portion defining a noncircular cross-section; and a porous layer carried by a peripheral surface area of said housing for promoting soft tissue ingrowth.
 14. The medical device of claim 13 further including an electroacoustic transducer mounted in said housing for projecting sound energy from said stud portion.
 15. The device of claim 14 further including at least one anchor carried by said housing configured for movement from a retracted position to a deployed position for engaging soft body tissue.
 16. In combination, a hearing aid housing and an instrument set for transporting said housing through a subcutaneous tunnel from a location behind a patient's pinnace to a subcutaneous location proximate to the patients ear canal, said combination comprising: said instrument set including an elongate shaft having a distal end configured for tunneling through soft body tissue to said subcutaneous location proximate to said ear canal, said shaft defining a lumen extending from an entrance opening to an exit opening at said distal end; said hearing aid housing configured for passage through said entrance opening, said lumen, and said exit opening; and a pusher member configured for axial movement in said shaft for pushing said housing through said lumen for implanting at said subcutaneous location.
 17. The combination of claim 16 wherein said lumen has a noncircular cross-section; and wherein said housing has a noncircular cross-section corresponding to said lumen cross-section.
 18. The combination of claim 16 further including means for threadedly engaging said pusher member and said shaft for enabling said pusher member to be rotated to axially advance said housing toward said exit opening.
 19. The device of claim 16 wherein said housing includes a body portion and a stud portion defining a longitudinally extending peripheral surface, and a shoulder between said body portion and said stud portion defining a laterally extending peripheral surface; and wherein a porous layer is formed on said longitudinally and/or laterally extending peripheral surfaces to promote tissue ingrowth.
 20. The combination of claim 16 further including: at least one anchor carried by said housing configured for movement between a retracted position and a deployed position; and wherein said anchor is held in said retracted position when said housing is in said lumen and is configured to automatically move to said deployed position when said housing is ejected from said shaft exit opening to engage subcutaneous tissue.
 21. The combination of claim 16 wherein said instrument set further includes: a hole forming tool having an elongate shank configured for removable insertion through said shaft lumen for forming a percutaneous hole opening into said patient's ear canal.
 22. The combination of claim 21 wherein said elongate shank has a cutting edge at its distal end for cutting said percutaneous hole.
 23. The combination of claim 22 wherein said shank is mounted for axial rotation to facilitate said cutting edge forming said percutaneous hole.
 24. The combination of claim 22 further including means for selectively advancing said cutting edge beyond said shaft distal end for cutting said percutaneous hole.
 25. The combination of claim 24 wherein said tool cutting edge defines a periphery for removing a plug of body tissue to form said percutaneous hole; and a rod movable relative to said cutting edge for removing any body tissue captured by said cutting edge.
 26. The combination of claim 24 wherein said shank is hollow and said cutting edge defines a periphery for capturing a plug of body tissue to form said percutaneous hole; and a rod axially movable through said shank for ejecting said plug into said patient's ear canal.
 27. The combination of claim 24 further including means for threadedly engaging said hole forming tool and said shaft whereby said tool can be axially rotated to incrementally advance said tool shank relative to said shaft.
 28. The combination of claim 22 wherein said hole forming tool and shaft are cooperatively configured to permit said tool to be axially rotated in a first mode to incrementally advance said tool shank relative to said shaft and in a second mode for freely spinning said shank in said shaft.
 29. The combination of claim 24 further including an anvil surface insertable into a patient's ear canal to allow said tool cutting edge to bear against said anvil surface to form said percutaneous hole.
 30. The combination of claim 29 including a speculum having first and second jaws operable to spread said patient's ear canal to increase visibility; and wherein said anvil surface is formed on at least one of said jaws.
 31. The combination of claim 16 wherein said shaft bears depth markings on its outer surface for indicating the magnitude of penetration of said shaft distal end.
 32. The combination of claim 16 wherein said instrument set further includes: an elongate obturator having a shank configured for removable insertion through said shaft lumen for closing said exit opening.
 33. The combination of claim 16 further including a movable door mounted on said shaft for normally closing the open distal end of said lumen, said door being configured to be opened by a tool passed through said lumen. 